It is commonly accepted that infection with either Human or Simian Immunodeficiency Virus (HIV or SIV, respectively) often results in mental abnormalities consistent with dementia. In humans this is called the AIDS Dementia Complex (ADC). As SIVmac affects rhesus macaques similarly to HIV in humans, it is considered a good animal model for both the acquired immunodeficiency syndrome (AIDS) and the ADC. The neuronal loss characteristic of late stages in ADC has not been shown in the SIV infected macaque model. Using high resolution proton NMR, we quantified N-Acetyl Aspartate (NAA), a recognized neuronal marker, in extracts of SIV infected and control macaque brain to determine the presence and extent of neuronal damage. A histological analysis was also performed and the results compared to NAA findings. We found a significantly reduced NAA in the SIV group compared to controls (2.9411.37; 6.2111.73 mmols/g wet weight, respectively). Interestingly, a NAA decrease was found in SIV infected animals at early stages of infection. Trends were found between the NAA content and histopathological lesions. These preliminary results show for the first time that SIV macaque model is a good one for the AIDS dementia complex. Confirmatory studies, as well as more detailed studies on the pathogenesis of neuronal loss are planned.